The emails said the worm had also shut down automatic systems and other hardware, as well as playing the hard-rock anthem.

"I am writing you to inform you that our nuclear program has once again been compromised and attacked by a new worm with exploits which have shut down our automation network at Natanz and another facility Fordo near Qom," the email read.

"According to the email our cyber experts sent to our teams, they believe a hacker tool Metasploit was used. The hackers had access to our VPN. The automation network and Siemens hardware were attacked and shut down. I only know very little about these cyber issues as I am scientist not a computer expert."

"There was also some music playing randomly on several of the workstations during the middle of the night with the volume maxed out. I believe it was playing 'Thunderstruck' by AC/DC."